Corrections...
From 2Hi-4hi with hubs unlocked: do not shift over 25 MPH (Nissan's advice), preferably under 10 MPH (avoid the noid, er, noise)
From 2hi-4hi with hubs still locked from last 4WD use (you have not reversed direction since shifting to 2hi): you can shift into 4WD at any speed, just be damn sure the hubs haven't unlocked if you're over 25 MPH!
From 4hi-2hi, shift at any speed. If you wish to unlock the hubs, stop and reverse direction for several feet afterwards.

From 2/4hi-4lo, you pretty much nailed it, but the 2-4 and 4-2 advice had a lot of bad info.

Brent
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